Back-up, or uninterruptable, power supplies have numerous uses in electronics applications to provide a back-up power source to a primary power system, such as AC line power or a primary battery system. One use for such systems is in high end computer applications, such as mainframes, minicomputers, supercomputers, network servers, and the like to prevent data loss during an interruption of the primary power to the computer.
For example, the AS/400 minicomputer system manufactured by International Business Machines Corp. includes an internal back-up power supply incorporated into a System Power Control Network (SPCN). The back-up power supply is required to provide back-up power suitable for permitting the system to download or store critical memory such that IPL time is significantly shortened after power is restored to the system.
Typically, as a result of an outage, critical operations are completed during a "conversion time" before a low power "sleep" or power saving mode is instituted. A back-up power supply must operate at a higher output during the conversion time, and at a lower output in the power saving mode.
It is important to test the batteries of a back-up power supply periodically to ensure their capability to handle a power outage sufficiently. Testing requires that the batteries be discharged so that performance data can be obtained therefrom. Conventionally, testing occurs either by using a dummy load or by switching the system load to the back-up power supply to increase the rate of discharge and thereby reduce testing time.
However, we have found that batteries have both high and low discharge capacities, both of which may vary independently from one another over time. In some instances, batteries may be able to handle high discharge during a conversion time, but may not be able to handle a long term low discharge in a "sleep" mode, or vice versa. Thus, we have found that a substantial need has arisen for testing both the high and low power capacities of batteries to ensure they can handle both high power backup and low power "sleep" modes.
Another concern associated with battery capacity testing is that such tests must execute in a reasonable amount of time to maximize system availability. Many conventional tests shut down line power to a system and run the system off the backup batteries to speed up battery discharge.
However, shutting down line power and relying completely on the batteries to supply system load during testing poses a significant concern as to system integrity should the batteries or any other back-up power supply components fail during the test. Thus, a substantial need has also arisen for a battery capacity test and system implementing the same which operates quickly but without compromising system integrity.